Method for constructing tooth surfaces of a dental prosthesis and for producing dental restorations

ABSTRACT

The invention relates to a method for constructing tooth surfaces of a dental prosthesis and for producing dental restorations, starting from a 3D data record of an upper mandible layout and a 3D data record of a lower mandible layout, each layout comprising a number of teeth arranged in each mandibular arch and the teeth of the upper mandible layout and the teeth of the lower mandible layout at intercuspation making contact with each other at multiple contact points. The contact surfaces are selected by approximation. Relevant surface pairs lying opposite one another are identified and are incorporated by an optimization algorithm into local minimum distances, taking into consideration surfaces that can slide past one another. This allows the desired contact points to be produced. Surfaces that have not been selected are not considered in the production of the points

TECHNICAL FIELD

The present invention relates to a method for construction of toothsurfaces of a dental prosthesis and for production of dentalrestorations, starting from a 3D data record of a maxilla layout and a3D data record of a mandible layout, each having multiple teethpositioned in the respective maxillary arch, wherein the teeth of themaxilla layout and the teeth of the mandible layout make contact witheach other at multiple contact points in intercuspation.

In addition, the invention relates to a computer program as well as adata medium and use of a computer [for] control of the computer program.

However, adequate allocation of the maxillary layouts to one another isnecessary to construct and produce tooth surfaces of dental prosthesisparts or to correct tooth positions.

PRIOR ART

Previous tools that are known and differ in convenience or precisionpull the opposing jaws strictly until they come in rigid contact,without taking the morphology into account, or must be controlledcompletely manually.

In buccal registration and in a bite registration, also known as asqueeze bite, an alignment of the two jaws to one another is calculatedby using one or more buccal pictures or bite registrations.

However, there are numeric limits to this method of setting arelationship.

The local resolution accuracy at the location of the picture necessarilydetermines, via the lever effect, the achievable accuracy of the fit onthe opposing location at a distance.

For example, if a local accuracy of 25 μm is assumed, an effect of 200μm is achieved on the opposite side of the jaw, which is, on theaverage, 8 cm away.

Doubling the scanning accuracy to 12 μm still creates an effect of 100μm on the opposite side.

One possible optimization is the use of multiple locations for buccalregistration or for the bite registration to ascertain the error.

This method can only be used when buccal registrations or squeeze biteinformation is available.

Another option for solving the problem is to allow, directly or afterpre-registration, free mobility of the jaws relative to one another,translating in 3 axes in space, i.e., longitudinally displaceably, androtationally about 3 axes in space.

The user must establish the contact situation freely by hand, purelyvisually, suspended in virtual 3D space, without thereby being able torely on a feeling of physical contact, which he had on a true model.

It is known from DE 10 2005 011 066 A1 to define three desired pointsmanually on a first and a second 3D data record of a model, wherein thepoints are contained in the first 3D data record as well as in thesecond, and to establish the correlation of the 3D data records.

Although a tooth surface of an opposing jaw may be included in a model,no different models are correlated.

It is a disadvantage that the desired maximal intercuspation cannot betaken into account in any of the cases known so far, as would happen innormal laboratory operation with plaster models clamped in anarticulator.

Therefore, the determination of the desired contact points lags behindmanual fitting and/or meets the methodological goals inadequately.

The object of the present invention is to provide a tool with which auser can create a desired contact situation for a given mandible andmaxilla layout and thus determine the allocation to one another, inorder to construct and produce tooth surfaces of dental prostheses partsor to correct tooth positions.

DESCRIPTION OF THE INVENTION

This object is achieved by the method according to the invention forconstruction of tooth surfaces of a dental prosthesis part and forproduction of dental restorations.

Starting from a 3D data record of a maxilla layout and a 3D data recordof a mandible layout, each having several teeth arranged in therespective arch of the jaw, wherein the teeth of the maxilla layout andthe teeth of the mandible layout have a multi-point contact having manycontact points, the allocation is carried out with contact optimization,in that

-   -   a common occlusal direction is automatically determined from the        3D data record of the maxilla layout and from the 3D data record        of the mandible layout,    -   the position of the teeth in the arch of the jaw is determined        automatically in the 3D data record of the maxilla layout and in        the 3D data record of the mandible layout,    -   surface elements that are at least approximately opposite one        another are identified automatically on at least one side on the        basis of the position of the teeth in the arch of the jaw, as        expected, and    -   on at least one side of the opposing surface elements, the        surface elements that are to come in contact are selected by the        user and/or approximately automatically;    -   on the other side of the opposing surface elements, the surface        elements that should come in contact are selected by the user        and/or are selected approximately automatically;    -   regions that are present on both sides of the opposing surface        elements are cut out and form surface pairs,    -   only the cut-out surface pairs are minimized in their distance        from one another by means of an optimization algorithm, such        that    -   the optimized allocation of the surface pairs can be transferred        to the entire 3D data record of the maxilla layout and to the        entire 3D data record of the mandible layout, and    -   the construction of tooth surfaces of a dental prosthesis part        as well as for production of dental restorations is done by        using 3D data records allocated in this way.

Advantageously only surface pairs that can slide past one another can betaken into account.

Falsification of surface pairs on which there cannot be any contact areprevented by this choice.

The optimization algorithm can advantageously provide a non-penetratingoverall layout of a 3D data record of a maxilla layout and a 3D datarecord of a mandible layout.

In optimization, it is possible to understand the working and theallocation of a real model due to this restriction.

An approximate allocation of the 3D data record of the maxilla layoutand the 3D data record of the mandible layout can be achievedadvantageously by pre-registration.

Pre-registration helps in defining the at least approximately opposingsurface elements.

The selected surface elements can advantageously be projectedautomatically onto the respective other side in the occlusal directionand thus selected.

Thus an automatic transfer from regions selected on only one side to theother side is possible.

Only the surface elements for which there is a further need foroptimization can advantageously be selected in a targeted manner.

The invention is thus based on a method in which the contact surfacesare marked approximately.

Unmarked surfaces are not taken into account for creating the contact.

On the whole, however, a non-penetrating overall layout is taken intoaccount, such as that which also occurs with true plaster models in thearticulator.

Relevant and opposing surface pairs are identified and are drawn intolocal distance minimums by optimization algorithm, taking into accountsurfaces that can slide past one another, which yields the desiredcontact points.

There may be a pre-registration of the jaws to simplify the allocationof the surfaces facing one another, which can be implemented in auser-friendly process with buccal registration, for example.

The invention also relates to a computer program, in particular aCAD/CAM program that can be controlled by the method according to theinvention.

The computer program is set up to display on a monitor at least one 3Ddata record of a maxilla layout or one 3D data record of a mandiblelayout, wherein the 3D data record has a mark indicating a state of thecomputer program into which the computer program can be brought byallocation of the 3D data records.

The invention further relates to a data medium which stores the computerprogram according to the invention.

It also relates to a computer for controlling a computer program.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention are illustrated in thedrawings and explained in greater detail in the following description.

In the figures:

FIG. 1 shows a 3D data record of a maxilla layout and a 3D data recordof the respective mandible layout in an approximate alignment with oneanother,

FIG. 2 shows a section through the two 3D data records approximatelyaligned with one another as a basic diagram with opposing surfaceelements identified,

FIG. 3 shows the selected surface elements on both sides considered foran allocation,

FIG. 4A shows regions delimited by projection in the occlusiondirection;

FIG. 4B shows the delimited regions from FIG. 4A as opposing markedsurface pairs;

FIG. 4 c shows the cutout regions from FIG. 4B used for theoptimization;

FIG. 5 shows a 3D data record of the maxilla after pre-registration withan initial contact situation,

FIG. 6 shows the 3D data record from FIG. 5 with selected surfaceelements,

FIG. 7 shows the 3D data record of the maxilla from FIG. 5 with acontact situation after optimization,

FIG. 8 shows a comparison of the maxilla as a plaster model with acontact situation in the articulator with maximal intercuspation,

FIG. 9 shows a data medium, a computer for carrying out the method and aprocessing machine for producing the dental prosthesis part.

EXAMPLE

In one embodiment of the present invention, a CAD/CAM program is carriedout on a device for construction of tooth surfaces of a dentalprosthesis part and producing dental restorations (for example, CEREC,AC+MC, XL from the present applicant).

The CAD/CAM program is set up to display on a screen a 3D data record 1,shown in FIG. 1, of a maxilla layout and a 3D data record 2 of amandible layout, each having multiple teeth 5, 6 arranged in therespective arch of the jaw 3, 4.

A common occlusal direction is determined automatically in the known wayfrom the 3D data record 1 of the maxilla layout and the 3D data record 2of the mandible layout.

In addition, the position of the teeth 5, 6 in the arch of the jaw 3, 4is determined automatically in a known way in the 3D data record 1 ofthe maxilla layout and in the 3D data record 2 of the mandible layout.

Since the teeth 5 of the maxilla layout 1 and the teeth 6 of themandible layout 2 have a multi-point contact with many contact points atintercuspation, which is unknown given separate detection of the 3D datarecords, an allocation must first be established by correlation of the3D data records.

The procedure for this is as follows: on the basis of the positions ofthe teeth 5, 6 in the arch of the jaw 3, 4, at least approximatelyopposite surface elements on at least one side, i.e., on one of the twojaw layouts, are identified automatically, as expected.

FIG. 2 shows a section through the two 3D data records 1, 2, which areapproximately aligned with one another, as a basic diagram with opposingsurface elements identified on teeth 5, 6.

FIG. 3 shows the selected surface elements 7-9 in question for anallocation on both sides, i.e., in the 3D data record 1 of the maxillalayout and in the 3D data record 2 of the mandible layout.

The surfaces which should come in contact are selected automatically orapproximately by the user.

On the other side of the opposing surface elements, the surface elementsthat should come in contact are selected by the user and/orapproximately automatically.

The surfaces can be determined in various ways: by user input,automatically with the help of the geometry of the tooth, in particularthe curvature, automatically with the help of bioenergetics,automatically on the basis of a height parameter, and certain surfaceportions can be included and certain surface portions can be excluded.

This choice can be made by the user, for example, by painting the 3Dmodel, clicking [and] drawing bordering lines, and can be transferredautomatically to the opposite jaw by pre-registration of the jawsrelative to one another.

There may be a trend toward “too many” surfaces, i.e., even those markedwith good contact already or, in a targeted manner, only those for whichthere is a further need for optimization.

FIG. 4A shows regions of allocated surface elements, which, after thechoice according to FIG. 3, can be delimited by an automatic projectiononto the respective other side in the occlusive direction, representedby the straight lines 10.

FIG. 4B shows the regions from FIG. 4A, delimited by the projection, asselected opposing surface pairs 11, 12, and

FIG. 4 c shows the cut-out regions from FIG. 4B, which are used for theoptimization and which are present on both sides of the opposing surfaceelements and form surface pairs 11, 12.

The contact is optimized by the fact that only the cut-out surface pairsare minimized in their distance from one another by means of anoptimization algorithm, e.g., a downhill-simplex method with a suitableevaluation function of the surfaces.

The contact layout is improved by the fact that only thesenon-contiguous regions are used instead of the model of the entire jaw.

The optimized allocation of the surface pairs is transferred to theentire 3D data record of the maxilla layout and to the entire 3D datarecord of the mandible layout.

FIGS. 5-8 show a screenshot of the surfaces drawn and the before/aftersituation compared with the actual genuine contact situation on theplaster model in the articulator.

It can be seen that it is even possible to resolve existing penetrationsof a pre-registration as well as to create the desired genuine contacts.

Furthermore, in comparison with the model in the articulator withgenuine contacts colored by means of contact film, this shows howrealistic and accurate the calculated result is.

FIG. 5 shows a 3D data record of the maxilla after pre-registration withan initial contact layout.

In the example, the one jaw half has too little contact and the otherjaw half tends to have too much contact, as indicated by the arrows andeven penetrations.

To carry out the method according to the invention, surface elements21-28 on the teeth are selected as shown in FIG. 6 in the 3D data recordfrom FIG. 5, on both sides of the jaw in the example, because there is aneed for optimization of the pre-registration on both sides.

FIG. 7 shows the 3D data record of the maxilla from FIG. 5 with acontact situation after optimization, where the contact points are againindicated by arrows.

A comparison with the contact situation of a maxilla, shown in FIG. 8,as a plaster model in the articulator at maximal intercuspation, shows acorrespondence at all the essential contact points, which are indicatedhere again by arrows.

On the basis of a model allocated in this way, the construction of toothsurfaces of a dental prosthesis part and for production of dentalrestorations can be carried out using 3D data records allocated in thisway.

A sequential procedure is conceivable, e.g., for creating a verticalincrease in occlusion, so that, e.g., even after successfully creating arestoration, this method can be applied again to a model scan, includingrestorations then calculated.

FIG. 9 shows a data medium 31 on which the computer program is stored, acomputer 32 having a monitor 33 and input means 34 for carrying out themethod, and a processing machine 35 for producing a dental prosthesispart 36, which is illustrated as a crown in a great magnification.

1. Method for construction of tooth surfaces of a dental prosthesis partas well as for producing dental restorations, starting from a 3D datarecord of a maxilla layout and a 3D data record of a mandible layout,each with a plurality of teeth arranged in the respective arch of thejaw, wherein the teeth of the maxilla layout and the teeth of themandible layout have a multi-point contact with numerous contact pointsin intercuspation, characterized in that the allocation is performedwith contact optimization, in that a common occlusal direction isautomatically determined from the 3D data record of the maxilla layoutand from the 3D data record of the mandible layout, the position of theteeth in the arch of the jaw is determined automatically in the 3D datarecord of the maxilla layout and in the 3D data record of the mandiblelayout, on the basis of the position of the teeth in the arch of thejaw, as expected, surface elements that are at least approximatelyopposite one another are identified automatically on at least one side,and on at least one side of the opposing surface elements, the surfaceelements that are to come in contact are selected by the user and/or areselected approximately automatically; on the other side of the opposingsurface elements, the surface elements that are to come in contact areselected by the user and/or are selected approximately automatically;regions that are present on both sides of the opposing surface elementsare cut out and form surface pairs, only the cut-out surface pairs areminimized in their distance from one another by means of an optimizationalgorithm, such that the optimized allocation of the surface pairs istransferred to the entire 3D data record of the maxilla layout and tothe entire 3D data record of the mandible layout, and the constructionof tooth surfaces of a dental prosthesis part as well as for productionof dental restorations is done by using 3D data records allocated inthis way.
 2. Method according to claim 1, characterized in that onlysurface pairs that can slide past one another are taken into account. 3.Method according to claim 1, characterized in that the optimizationalgorithm supplies a non-penetrating overall layout of a 3D data recordof a maxilla layout and of a 3D data record of a mandible layout. 4.Method according to claim 1, characterized in that an approximateallocation of the 3D data record of the maxilla layout and of the 3Ddata record of the mandible layout is accomplished via pre-registration,in particular via buccal registration.
 5. Method according to claim 1,characterized in that the selected surface elements in the occlusaldirection are projected automatically onto the respective other side,and the regions that are present on both sides of the opposing surfaceelements are cut out and form surface pairs.
 6. Method according toclaim 1, characterized in that only the surface elements for which thereis a need for further optimization are selected in a targeted manner. 7.Computer program, characterized in that it can be controlled by means ofa method according to claim
 1. 8. Computer program according to claim 7,characterized in that it is a CAD/CAM program.
 9. Computer programaccording to claim 7, characterized in that it is set up to display on amonitor at least one 3D data record of a maxilla situation or a 3D datarecord of a mandible layout, wherein the 3D data record has a markindicating a state of the computer program into which the computerprogram can be brought by allocation of the 3D data records.
 10. A datamedium, characterized in that it stores a computer program according toclaim
 7. 11. Use of a computer for controlling a computer programaccording to claim 7.